Focal plane arrays (FPAs) that detect infrared (IR) radiation, such as thermal IR radiation, are used by IR cameras to provide thermal images. For example, thermal radiation passing through an optical path of an IR camera is received by IR detectors of the FPA, which provide image data for pixels of thermal images.
The quality of thermal images provided by FPAs may be degraded due to non-uniform responses among the individual IR detectors to incident IR radiation. Because the magnitude of the non-uniformity may be large in comparison to the magnitude of the actual response due to the incident IR radiation, various techniques are typically used to compensate for the non-uniformity and obtain a desirable signal-to-noise ratio.
For example, in some conventional IR imaging devices, an FPA may be calibrated over one or more levels of photon flux by inserting a mechanical shutter that can selectively be moved into the optical path of the IR camera. The FPA takes one or more data frames or snapshots of the shutter to calibrate its response, and the collected data may then be used to calibrate the FPA to provide a more uniform response. Such a mechanical shutter may also be found in some non-thermal (e.g., visible light) imaging devices having charge-coupled devices (CCDs) or complementary metal-oxide (CMOS) sensors, for example, for calibration and/or imaging capturing purposes.
An automatic mechanical shutter requires a shutter blade (e.g., a shutter paddle), an actuator (e.g., a motor) and an associated drive train to move the shutter blade in and out of the optical path. As such, an automatic mechanical shutter, if integrated into or otherwise provided in an imaging device, may increase the size, complexity, and cost of the imaging device, which is undesirable especially for compact imaging devices. Furthermore, mechanical components such as motors and associated drive trains of automatic mechanical shutters are more prone to wear and tear than solid state components such as a FPA, and thus adversely affect the overall reliability and longevity of imaging devices that rely on automatic mechanical shutters.